The wedge-tailed eagle (Aquila audax), sometimes known as the eaglehawk (both misnomers, as it is not a hawk, and its tail is shaped more like a diamond), is the largest bird of prey in Australia, and is also found in southern New Guinea. It has long, fairly broad wings, fully feathered legs and an unmistakable diamond-shaped tail. Because of both its tail and its size—it is one of the largest birds of prey in the world—it can be identified at a glance as a "Wedgie" even by the non-expert.

The wedge-tailed eagle is one of twelve species of large predominantly dark-coloured booted eagles in the genus Aquila found worldwide. A large brown bird of prey, it has a wingspan of up to 2.27 m (7 ft 5 in) and a length up to 1.06 m (3 ft 6 in).[2]

The female wedge-tailed eagle weighs between 3 and 5.77 kg (6.6 and 12.7 lb), while the smaller males weigh 2 to 4 kg (4.4 to 8.8 lb).[2][3] Length varies between 81 and 106 cm (32 and 42 in) and the wingspan typically is between 182 and 232 cm (6 ft 0 in and 7 ft 7 in).[2][3] In 1930, the average weight and wingspans of 43 birds was 3.4 kg (7.5 lb) and 204.3 cm (6 ft 8 in).[4] The same average figures for a survey of 126 eagles in 1932 were 3.63 kg (8.0 lb) and 226 cm (7 ft 5 in), respectively.[5] The largest wingspan ever verified for an eagle was for this species. A female killed in Tasmania in 1931 had a wingspan of 284 cm (9 ft 4 in), another female measured barely smaller at 279 cm (9 ft 2 in).[5] Reported claims of eagles spanning 312 cm (10 ft 3 in) and 340 cm (11 ft 2 in) were deemed to be unreliable.[5] This eagle's great length and wingspan place it among the largest eagles in the world but its wings, at more than 65 cm (26 in), and tail, at 45 cm (18 in), are both unusually elongated for its body weight and 8-9 other eagle species regularly outweigh it.[3]

Young eagles are a mid-brown colour with slightly lighter and reddish-brown wings and head. As they grow older, their colour becomes darker, reaching a dark blackish-brown shade after about ten years (birds in Tasmania are usually darker than those on the mainland). Adult females tend to be slightly paler than males. Although it rarely needs to be distinguished from other Aquila eagles, its long, wedge-shaped tail is unique to this species.

Its range and habitat sometimes overlap with the white-bellied sea eagle, which is similar in size and shape and also has a somewhat diamond-shaped tail, although rather smaller and less distinctive. In silhouette and poor light, the two can look somewhat similar. Closer examination reveals the belly colour or tail size to distinguish the two.

Wedge-tails are found throughout Australia, including Tasmania, and southern New Guinea in almost all habitats, though they tend to be more common in lightly timbered and open country in southern and eastern Australia. In New Guinea, the birds can be found in the Trans Fly savanna and grasslands.

As the breeding season approaches, a pair of wedge-tailed eagles will perch close to each other and preen one other. They also perform dramatic aerobatic display flights together over their territory. Sometimes the male dives down at breakneck speed towards his partner. As he pulls out of his dive and rises just above her on outstretched wings, she either ignores him or turns over to fly upside down, stretching out her talons. The pair may then perform a loop-the-loop. The wedge-tailed eagle usually nests in the fork of a tree between one and thirty metres above the ground, but if there are no suitable sites, it will nest on a cliff edge.

Before egg laying, both birds will either destroy the large stick nest or add new sticks and leaf lining to an old nest. Nests can be 2–5 metres deep and 2–5 metres wide. The female usually lays two eggs, which are incubated by both sexes. After about 45 days, the chicks hatch. At first, the male does all the hunting. When the chicks are about 30 days old, the female stops brooding them and joins her mate to hunt for food.

The young wedge-tailed eagles depend on their parents for food for up to six months after hatching. They leave only when the next breeding season approaches.

They are highly aerial, soaring for hours on end without wingbeat or effort, regularly reaching 1,800 metres (5,900 ft) and sometimes considerably higher. The purpose of this very high flight is unknown. Their keen eyesight extends into the infrared and ultraviolet bands. This helps them spot prey and allows them to see rising thermals, which they can use to gain altitude while expending little energy.

They display considerable adaptability, and have sometimes been known to team up to hunt large red kangaroos, to cause goats to fall off steep hillsides and injure themselves, or to drive flocks of sheep or kangaroos to isolate a weaker animal.[7]

Carrion is a major diet item also: wedge-tails can spot the activity of Australian ravens (sometimes known as crows) around a carcass from a great distance, and glide down to appropriate it. Wedge-tailed eagles are often seen by the roadside in rural Australia, feeding on animals that have been killed in collisions with vehicles.

This impressive bird of prey spends much of the day perching in trees or on rocks or similar exposed lookout sites such as cliffs from which it has a good view of its surroundings. Now and then, it takes off from its perch to fly low over its territory. During the intense heat of the middle part of the day, it often soars high in the air, circling up on the thermal currents that rise from the baking ground below. Each pair occupies a home range, which may extend from as little as 9 km2 (3.5 sq mi) to more than 100 km2 (39 sq mi). Within this home range lies a breeding territory around the nest. The eagle patrols the boundary of this home range and advertises its ownership with high-altitude soaring and gliding flights. It may defend its territory by diving on intruders. Adults are avian apex predators and have no natural predators but must defend their eggs and nestlings against nest predators such as corvids, currawongs, or other wedge-tailed eagles and in Tasmania there is often conflict with the white-bellied sea eagle over nest sites.

The wedge-tailed eagle is the only bird that has a reputation for attacking hang gliders and paragliders (presumably defending its territory). There are recorded cases of the birds damaging the fabric of these gliders with their talons.

Parks and Wildlife Service Northern Territory (Australia) use the wedge-tailed eagle, superimposed over a map of the Northern Territory, as their emblem. The New South Wales Police Force emblem contains a wedge-tailed eagle in flight, as does the Northern Territory Correctional Services. La Trobe University in Melbourne also uses the wedge-tailed eagle in its corporate logo and coat of arms.[10] The Royal Australian Air Force and Australian Air Force Cadets Use the Wedge-Tailed on their badge.[11] Australian Army 2nd Cavalry Regiment Early in 1967, the 2nd Cavalry Regiment received its new badge, a wedge tailed eagle swooping, carrying a lance bearing the motto "Courage" in its talons. The regiment's mascot is a Wedge-tailed Eagle named "Courage". Since its formation, there have been two, Courage I and Courage II. In 1997, while on flight training with his handlers, Corporal Courage II refused to cooperate and flew away, not being found for two days following an extensive search. He was charged with being AWOL and reduced to the rank of Trooper. He was promoted back to Corporal in 1998.[12][13]

The West Coast Eagles AFL football club uses a wedge-tailed eagle as their club mascot.